A $50,000 reward is now being offered by the family of a college baseball player who was shot and killed in San Francisco's Aquatic Park six months ago.

The father of Calvin Riley made the announcement during a candlelight vigil in San Mateo's Central Park, hoping that the news would help stimulate new leads in the case.

"Losing my best friend, my buddy, my boy... I just can't say it enough," said Sean Riley, Calvin's father, his voice cracking and eyes welling with tears. " I miss him, I'd do anything to bring him back. I need someone to come forward, I'm begging someone to come forward , someone has to know something,"

20-year-old Calvin Riley, a baseball player at Stockton's Delta Community College, was shot in the back while playing Pokemon Go near Ghirardelli Square on August 6th shortly before 10 p.m. He was doing some sightseeing with a friend who was visiting from Boston. Calvin's killer has still not been found.

Tonight, 200 people lit candles, prayed and spoke about the man they said changed lives for the better. "Your son was a hero to so many of us," said Father Joe Bradley.

"Calvin Michael Riley was the older brother I never had," said former high school teammate Thomas McCarthy, as he choked back tears.

Friends say Calvin was a mentor to many of the younger players on the Junipero Serra baseball team where he attended high school.

Investigators believe his killing was random.

"I never saw him yell or get mad at anyone, he was the nicest kid in the world. I will forever smile for C.R. 9- and I love you, Cal and I miss you," cried McCarthy.

"9" was Calvin's jersey number, which Serra High retired after his murder.

"No one will ever wear number nine again," said Serra Baseball Coach Craig Gianinno. "There will forever be a Calvin Riley award honoring future players that come through that represent what Calvin represented. Calvin worked at practice but he did even more work when no one was watching. He loved the camaraderie of his brothers, loved being a [Serra] Padre and his brothers truly loved him."

"We're exhausting every lead that we can get our hands on," said Lt. Timothy Hodge, with the United States Park Police, the lead agency on the case.

In September, Park Police released a sketch of a possible suspect, described as an African American orLlatino male in his 20s to 30s.

They've identified two vehicles of interest: a 2013 or 2014 white Hyundai Sonata driven by a white female with blonde hair, as well as a dark-colored car, unknown make and model.

Calvin's dream was to someday play professional baseball. His father said he was well on his way to play baseball at a Division One College that fall.

"With every rep we take in the weight room, or every swing we take in the cage or every ground ball we take on the field or every smile we make, we do it for Cal," said former Serra teammate Patrick McCarthy.

Calvin's family hopes the reward money shines a new light on the case so they can finally get justice for their son.

Sean Riley closed the ceremony by saying, "Hug your kids a little tighter and tell 'em you love 'em one more time, cause I would do anything... anything to hug Calvin one more time and tell him I love him."